1. Field of the Invention
The present invention generally relates to a shared radio communication system established by a plurality of radio communication systems, communication terminals capable of utilizing each of radio communication services provided by such a plurality of radio communication systems, and IC card writers for writing radio communication software into IC cards to be attached to communication terminals.
2. Description of the Related Art
A variety of radio communication systems have been developed recently. These radio communication systems provide different services and have different service areas. Accordingly users have to use different communication terminals in order to utilize different radio communication systems. It is, however, inconvenient to carry a plurality of communication terminals, and therefore one communication terminal (referred to as “shared communication terminal” hereinafter) that can be shared or can be commonly used for a plurality of radio communication systems has been developed recently.
Such conventional shared communication terminals, however, have one hardware set that can be commonly used for a plurality of predetermined radio communication systems. The conventional shared communication terminals cannot be utilized for other radio communication systems for which the built-in hardware is not compatible.
Radio communication software packages necessary for utilizing each communication service are pre-installed in the conventional communication terminals and cannot be rewritten. Therefore, users have to purchase a new communication terminal in order to utilize a new communication service provided by a new radio communication system.
One another approach is shown in Japanese Patent Laid-open Publication No. 11-73095, in which a converter provided between a base station and communication terminals is used for a plurality of radio communication services. In this technology, a special converter is provided separately from communication terminals, introducing complexity and inconvenience.